The king was also severely developmentally delayed. He was breastfed until he was five, and never received any formal education. His speech was delayed until he was four, and he couldn’t walk until the age of eight. Even as an adult, his communication was muffled and hardly comprehensible. He was also impotent, so his inability to procreate ended the Habsburg’s hold on the Spanish crown when the king died at age 39 in 1700.

Desperate to save her son's life, Alexandra sought mystical intervention in the form of Rasputin, the "Mad Monk.” Inviting a lascivious man like Rasputin, known for his tastes for alcohol and lovers of both sexes, didn’t go over well with the aristocracy. The Russian rulers, however, were convinced that Rasputin’s treatments were effective in saving their son.

The mystic Rasputin gained greater influence at court, wielding increasing power over the lives of the royals and surreptitiously governing Russia. The disorder in the royal house and the questionable company the rulers kept helped spur the Russian Revolution of 1917, and as a result, the entire royal family was executed.

Nor was Alexei the only relative of Queen Victoria's to be afflicted with hemophilia:

"The 19th century British monarch's son Leopold, Duke of Albany, died from blood loss after he slipped and fell. Her grandson Friedrich bled out at age 2; her grandsons Leopold and Maurice, at ages 32 and 23, respectively

Although his legacy is as the golden boy pharaoh of ancient Egypt, DNA tests of King Tut's mummified corpse show that this ruler of Egypt circa 1300 BC was actually a feeble-bodied genetic misfit, owing to the Egyptian royal tradition of brothers and sisters marrying one another. King Tutankhamun took the throne at age 10 and survived only until the age of 19. He likely had a cleft palate, a club foot, and scoliosis, as well as an elongated, deformed skull. He probably required a cane to walk and evidence suggests he suffered from malaria because of a weak immune system.

Egyptian pharaohs revered sibling marriage, influenced by the legend that the god Osiris married his sister, Isis, to maintain a pure bloodline. There were even instances of "double niece" marriages (defined as when a man marries a girl who was the offspring of his brother and sister).

An Hereditary Blue Urine Disease May Have Driven King George III Insane

George III routinely checked out from his royal duties to escape to seclusion and private recovery at Kew Palace. He was prone to babbling delusions in his later life and subjected to extreme treatments including strait-jackets, leeching, and ice baths to calm him. Modern medical testing shows porphyria was common in the highly inbred House of Hanover, to which King George III belonged.

George III spent the final decade of his reign in hiding and eventually lost his vision and hearing

The mentally unstable Queen Maria I was married to her uncle, who had his own share of mental issues. Over the course of her rule from 1777 to 1816, she watched two of her children die of smallpox, as well as her son-in-law and grandson, all of which is partially blamed for her decline into insanity. Known as the Mad Queen, she was given to delusional fits and religious obsessions, and often dressed as a little girl. Maria spent much time in seclusion, but her howling could be heard throughout the royal estate. Her grip on sanity was so feeble that by 1799 her son John was the unofficial ruler while she remained queen in title only. Eventually the family fled to Brazil during the Napoleonic Wars, and Maria I died in a convent.

Mental illness ran through Maria I's family, afflicting both her grandfathers. The family was also extremely inbred: not only was Maria I married to her uncle, but Maria's eldest son Joseph married his aunt

The Inbred Empress Elisabeth of Austria Was Plagued By Anorexia And Depression

Nicknamed "Sisi," the beautiful but troubledEmpress Elisabeth I came from a long line of royals known for their strange behavior, including the notoriously eccentric King Ludwig II of Bavaria. At age 16, she married her cousin Franz Joseph and became empress. This cousin was obsessed with Sisi, but she did not love him back and she hated his mother (her aunt), the strict and overbearing Archduchess Sophie, who installed one of her friends as lady-in-waiting to spy on Sisi.

Sisi was known for being extremely beautiful, but as she grew older and more anxious and depressed, she became anorexic and developed an elaborate, obsessive beauty regimen intended to keep her looking young and thin. She starved herself, exercised excessively, and forbade anyone to paint her portrait once she was no longer young. She traveled extensively (largely to avoid her husband), wrote tons of moody poetry, and talked of suicide, before she was murdered by an anarchist in 1898.